Ex Brit on going Ome!
The first time back in the UK with my then new Wife, 1992, wore the things I wear most always, 511 pants.
The Mother in Law said I was to old to wear those pants, all the kids wear them! I had wore them for ever! Velcro down pockets, carry local cash, change in left front pocket, twenty's in left side, 50s in right, learn to wiggle one out when needed, do not flash wallet, you do not need to use a wallet, renting a car? standard tranny, Diesel 4 door, get an extra key, place in bottom of phone pocket (in case) make sure your cell phone works over there, or pick up cheepy.
Sneakers are fine now, I always wore them, Liverpool accent also works.
At over 70 last time in England, City Stick was acceptable, lots of Brits have walking sticks past a certain age, damp place. Plane has no problem either.
I can not live without a pen knife, buy a little cheap one, leave it behind.
Walked everywhere with my Wife, her on one hand, walking stick in the other one, was left alone. Got picked for a "Yank" till I spoke.
Hiking style jackets both of us, Browning, dark green, waterproof, will fold up small, never out of place, rains a lot.
Green back pack, snacks, water, shopping stuff all fit, leaves hands free.
Learn to ask polite English/Liverpool type questions, like "Do you like Hospital food?" Well maybe not.